Abstract:

A thin film can be formed on a substrate at a low temperature with a
practicable film-forming rate. There is provided a semiconductor device
manufacturing method for forming an oxide or nitride film on a substrate.
The method comprises: exposing the substrate to a source gas; exposing
the substrate to a modification gas comprising an oxidizing gas or a
nitriding gas, wherein an atom has electronegativity different from that
of another atom in molecules of the oxidizing gas or the nitriding gas;
and exposing the substrate to a catalyst. The catalyst has acid
dissociation constant pKa in a range from 5 to 7, but a pyridine is
not used as the catalyst.

Claims:

1. A semiconductor device manufacturing method for forming an oxide or
nitride film on a substrate, comprising:exposing the substrate to a
source gas;exposing the substrate to a modification gas comprising an
oxidizing gas or a nitriding gas, wherein an atom has electronegativity
different from that of another atom in molecules of the oxidizing gas or
the nitriding gas; andexposing the substrate to a catalyst,wherein the
catalyst has acid dissociation constant pKa in a range from 5 to 7,
but a pyridine is not used as the catalyst.

2. The semiconductor device manufacturing method of claim 1, wherein the
exposing of the substrate to the source gas and the exposing of the
substrate to the catalyst are simultaneously performed, and the exposing
of the substrate to the modification gas and the exposing of the
substrate to the catalyst are simultaneously performed.

3. The semiconductor device manufacturing method of claim 1, further
comprising removing the source gas, the oxidizing gas, or the nitriding
gas that remains, wherein the substrate is exposed to the source gas, the
oxidizing gas, or the nitriding gas in a state where the source gas and
the oxidizing gas or the nitriding gas are not mixed with each other.

5. The semiconductor device manufacturing method of claim 4, wherein the
catalyst is one of aminopyridine, picoline, piperazine, and lutidine.

6. The semiconductor device manufacturing method of claim 1, wherein the
oxidizing gas is a substance having OH bonds, and the nitriding gas is a
substance having NH bonds.

7. A semiconductor device manufacturing method comprising:exposing a
substrate placed in a process chamber to a source gas;exposing the
substrate placed in the process chamber to a modification gas comprising
an oxidizing gas or a nitriding gas, wherein an atom has
electronegativity different from that of another atom in molecules of the
oxidizing gas or the nitriding gas; andexposing the substrate placed in
the process chamber to a catalyst,wherein the exposing of the substrate
to the source gas, the exposing of the substrate to the modification gas,
and the exposing of the substrate to the catalyst are performed while
heating the substrate, so as to form an oxide or nitride film on the
substrate,wherein in the exposing of the substrate to the catalyst, the
process chamber is kept at a pressure lower than a vapor pressure of a
byproduct corresponding to a surface temperature of the substrate, the
byproduct being produced by a reaction between the catalyst and the
source gas and starting to sublimate at the vapor pressure,wherein the
sublimated byproduct is exhausted to an outside area of the process
chamber.

8. The semiconductor device manufacturing method of claim 7, wherein the
process chamber is kept at a temperature equal to or lower than
200.degree. C.

9. The semiconductor device manufacturing method of claim 8, wherein the
process chamber is kept at about 100.degree. C.

10. A substrate processing apparatus comprising:a process chamber
configured to accommodate a substrate;a first gas supply system
configured to supply a source gas to the process chamber;a second gas
supply system configured to supply at least one of an oxidizing gas and a
nitriding gas to the process chamber, wherein an atom has
electronegativity different from that of another atom in molecules of the
oxidizing gas and the nitriding gas;a third gas supply system configured
to supply a catalyst to the process chamber, wherein the catalyst has
acid dissociation constant pKa in a range from about 5 to about 7
but a pyridine is not used as the catalyst; anda control unit configured
to control the first to third gas supply systems,wherein the control unit
controls the first to third gas supply systems to expose a surface of the
substrate to a mixture of the source gas and the catalyst and then to a
mixture of the catalyst and at least one of the oxidizing gas and the
nitriding gas, so as to form a oxide or nitride film on the substrate.

Description:

CROSS-REFERENCE TO RELATED PATENT APPLICATION

[0001]This U.S. non-provisional patent application claims priority under
35 U.S.C. §119 of Japanese Patent Application Nos. 2009-034256,
filed on Feb. 17, 2009, and 2010-007961, filed on Jan. 18, 2010, in the
Japanese Patent Office, the entire contents of which are hereby
incorporated by reference.

BACKGROUND OF THE INVENTION

[0002]1. Field of the Invention

[0003]The present invention relates to a semiconductor device
manufacturing method and a substrate processing apparatus, and more
particularly, to technology for processing a substrate at a low
temperature.

[0004]2. Description of the Prior Art

[0005]A film can be formed on a substrate by a method such as a chemical
vapor deposition (CVD) method in which a plurality of kinds of sources
including a plurality of constitutional elements of a film are
simultaneously supplied to a substrate placed in a process chamber; and
an atomic layer deposition (ALD) method in which a plurality of kinds of
sources are alternately supplied to a substrate (for example, refer to
Patent Document 1).

[0006]However, in such a method, a film may have to be formed at a high
temperature of about 700° C. for obtaining a practical film
growing rate; however, high-temperature processing increases the
possibility of impurity rediffusion, and thus low-temperature processing
has been required.

[0009]As means for low temperature processing, use of catalysts can be
considered. Since a catalyst reduces the activation energy of a source
gas applied to a substrate, the process temperature can be reduced.
Examples of film forming methods using a catalyst include U.S. Pat. No.
6,090,442, and U.S. Patent Application Publication Nos. 2004-40110 and
2008-141191. The example Patents disclose exemplary methods of using
pyridine (C5H5N) as a catalyst; however, since pyridine causes
environmental pollution such as air pollution, use of pyridine is
regulated by a law.

SUMMARY OF THE INVENTION

[0010]An object of the present invention is to provide a semiconductor
device manufacturing method and a substrate processing apparatus by which
a film can be formed on a substrate at a low temperature.

[0011]According to an aspect of the present invention, there is provided a
semiconductor device manufacturing method for forming an oxide or nitride
film on a substrate, the semiconductor device manufacturing method
comprising: exposing the substrate to a source gas; exposing the
substrate to a modification gas comprising an oxidizing gas or a
nitriding gas, wherein an atom has electronegativity different from that
of another atom in molecules of the oxidizing gas or the nitriding gas;
and exposing the substrate to a catalyst, wherein the catalyst has acid
dissociation constant pKa in a range from 5 to 7, but a pyridine is
not used as the catalyst.

[0012]According to another aspect of the present invention, there is
provided a semiconductor device manufacturing method comprising: exposing
a substrate placed in a process chamber to a source gas; exposing the
substrate placed in the process chamber to a modification gas comprising
an oxidizing gas or a nitriding gas, wherein an atom has
electronegativity different from that of another atom in molecules of the
oxidizing gas or the nitriding gas; and exposing the substrate placed in
the process chamber to a catalyst, wherein the exposing of the substrate
to the source gas, the exposing of the substrate to the modification gas,
and the exposing of the substrate to the catalyst are performed while
heating the substrate, so as to form an oxide or nitride film on the
substrate, wherein in the exposing of the substrate to the catalyst, the
process chamber is kept at a pressure lower than a vapor pressure of a
byproduct corresponding to a surface temperature of the substrate, the
byproduct being produced by a reaction between the catalyst and the
source gas and starting to sublimate at the vapor pressure, wherein the
sublimated byproduct is exhausted to an outside area of the process
chamber.

[0013]According to another aspect of the present invention, there is
provided a substrate processing apparatus comprising: a process chamber
configured to accommodate a substrate; a first gas supply system
configured to supply a source gas to the process chamber; a second gas
supply system configured to supply at least one of an oxidizing gas and a
nitriding gas to the process chamber, wherein an atom has
electronegativity different from that of another atom in molecules of the
oxidizing gas and the nitriding gas; a third gas supply system configured
to supply a catalyst to the process chamber, wherein the catalyst has
acid dissociation constant pKa in a range from about 5 to about 7
but a pyridine is not used as the catalyst; and a control unit configured
to control the first to third gas supply systems, wherein the control
unit controls the first to third gas supply systems to expose a surface
of the substrate to a mixture of the source gas and the catalyst and then
to a mixture of the catalyst and at least one of the oxidizing gas and
the nitriding gas, so as to form a oxide or nitride film on the
substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a schematic perspective view illustrating a substrate
processing apparatus that can be properly used according to an embodiment
of the present invention.

[0015]FIG. 2 is a schematic view illustrating a process furnace and
surrounding members that can be properly used according to an embodiment
of the present invention, in which a vertical section of the process
furnace is illustrated.

[0016]FIG. 3 is a sectional view taken along line A-A of the process
furnace of FIG. 2 that can be properly used according to an embodiment of
the present invention.

[0017]FIG. 4 is a view illustrating a relationship between film-forming
rate and film-forming temperature when a silicon film is formed using
NH3 as a catalyst.

[0018]FIG. 5 is a view illustrating a sequence for forming a silicon oxide
film according to a first embodiment of the present invention.

[0019]FIG. 6A and FIG. 6B are views illustrating models of silicon oxide
film formation according to the first embodiment of the present
invention.

[0020]FIG. 7 is a view illustrating pressure variations in the film
forming sequence of the first embodiment of present invention.

[0021]FIG. 8 is a view illustrating structures of NH3 and catalysts
having pKa similar to that of NH3.

[0022]FIG. 9 is a view illustrating a vapor pressure curve of NH4Cl.

[0023]FIG. 10 is a view illustrating a sequence for forming a silicon
oxide film according to a second embodiment of the present invention.

[0024]FIG. 11 is a view illustrating a relationship between supply time of
SiCl4 and pyridine and film thickness.

[0025]FIG. 12 is a view illustrating a film thickness obtained by
supplying SiCl4 at a constant rate and pyridine at a varying rate.

[0026]FIG. 13 is a view illustrating a relationship between supply time of
H2O and pyridine and film thickness.

[0027]FIG. 14 is a view illustrating a film thickness obtained by
supplying H2O at a constant rate and pyridine at a varying rate.

[0028]FIG. 15 is a view illustrating models of silicon oxide film
formation according to the second embodiment of the present invention.

[0029]FIG. 16 is a view for comparing numbers of particles on a wafer.

[0030]FIG. 17 is a view illustrating a vapor pressure curve of a pyridine
salt.

[0031]FIG. 18 is a view for comparing film-forming rates.

[0032]FIG. 19 is a view illustrating structures of catalysts having
pKa in the range from 5 to 7.

[0033]FIG. 20 is a view illustrating structures of catalysts having high
pKa.

[0034]FIG. 21 is a view illustrating structure of catalysts having low
pKa.

[0035]FIG. 22 is a view illustrating models of silicon oxide film
formation according to a fourth embodiment of the present invention.

[0036]FIG. 23 is a view illustrating a relationship between particle
number and film-forming temperature when pyridine is used as a catalyst.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037]Although many kinds of catalysts can be used, the inventers have
selected catalysts according to the acid dissociation constant (pKa)
of the catalysts which is a quantitative index indicating the strength of
an acid. Although a dissociation reaction by which hydrogen ions are
generated from an acid can be expressed by an equilibrium constant
Ka or the negative common logarithm of Ka (pKa=-log10
Ka), only the negative common logarithm pKa is used herein for
consistency. An acid having a low pKa is a strong acid.

[0038]For example, NH3 can be used as a catalyst. NH3 can be
used as a catalyst because a nitrogen (N) atom of a NH3 molecule has
a lone pair of electrons that attracts a hydrogen (H) atom. The degree of
a force attracting hydrogen can be expressed by acid dissociation
constant (pKa), and the pKa of NH3 is about 11. High
pKa indicates a strong hydrogen (H) attracting force.

[0039]The present invention is provided based on the knowledge of the
inventors. Hereinafter, a first embodiment of the present invention,
which is an embodiment of the present invention, will be described with
respect to the attached drawings.

[0040][Overall Structure of Apparatus]

[0041]In the current embodiment of the present invention, a substrate
processing apparatus of the present invention is configured as an example
of a semiconductor manufacturing apparatus that performs a processing
process in a method of manufacturing a semiconductor device integrated
circuit (IC). In the following description, the use of a vertical
apparatus, which is configured to perform a processing process on a
substrate such as an oxidation process, a diffusion process, or a
chemical vapor deposition (CVD) process, will be described as an example
of a substrate processing apparatus. FIG. 1 is a schematic perspective
view illustrating a substrate processing apparatus that can be properly
used according to an embodiment of the present invention. However, the
present invention is not limited to the substrate processing apparatus of
the current embodiment. For example, the present invention can be applied
to other substrate processing apparatuses such as a substrate processing
apparatus having a single-wafer type, hot wall type, or cold wall type
process furnace

[0042]As shown in FIG. 1, in a substrate processing apparatus 101,
cassettes 110 are used to accommodate substrates such as wafers 200, and
the wafers 200 may be silicon wafers. The substrate processing apparatus
101 includes a case 111, in which a cassette stage 114 is installed. The
cassettes 110 are designed to be carried onto the cassette stage 114, or
carried away from the cassette stage 114, by an in-process carrying unit
(not shown).

[0043]On the cassette stage 114, a cassette 110 is placed by an in-process
carrying device in a manner such that wafers 200 are vertically
positioned in the cassette 110 and a wafer hole of the cassette 110 is
pointed upward. The cassette stage 114 is configured so that the cassette
110 is rotated 90° counterclockwise in a longitudinal direction to
the backward of the case 111 so as to horizontally orient the wafers 200
of the cassette 110 and point the wafer hole of the cassette 110 to the
backward of the case 111.

[0044]Near the center part of the case 111 in a front-to-back direction, a
cassette shelf 105 is installed. The cassette shelf 105 is configured so
that a plurality of cassettes 110 can be stored in multiple rows and
columns.

[0045]At the cassette shelf 105, a transfer shelf 123 is installed to
store cassettes 110, which are carrying objects of a wafer transfer
mechanism 125.

[0046]At the upside of the cassette stage 114, a standby cassette shelf
107 is installed, and configured to store standby cassettes 110.

[0047]Between the cassette stage 114 and the cassette shelf 105, a
cassette carrying device 118 is installed. The cassette carrying device
118 includes a cassette elevator 118a capable of moving upward and
downward while holding a cassette 110, and a cassette carrying mechanism
118b. The cassette carrying device 118 is configured to carry cassettes
110 among the cassette stage 114, the cassette shelf 105, and the standby
cassette shelf 107 by continuous motions of the cassette elevator 118a
and the cassette carrying mechanism 118b.

[0048]At the backside of the cassette shelf 105, the wafer transfer
mechanism 125 is installed. The wafer transfer mechanism 125 includes a
wafer transfer device 125a capable of rotating or linearly moving wafers
200 in a horizontal direction, and a wafer transfer unit elevator 125b
configured to move the wafer transfer device 125a upward and downward. At
the wafer transfer device 125a, tweezers 125c are installed to pick up
wafers 200. The wafer transfer mechanism 125 is configured to pick up
wafers 200 using the tweezers 125c, and charge the wafers 200 into a boat
217 or discharge the wafer 200 from the boat 217, by continuous motions
of the wafer transfer device 125a and the wafer transfer unit elevator
125b.

[0049]At the upside of the rear part of the case 111, a process furnace
202 is installed to perform a heat treatment process on wafers 200, and
the bottom side of the process furnace 202 is configured to be opened and
closed by a furnace port shutter 147.

[0050]At the downside of the process furnace 202, a boat elevator 115 is
installed to move the boat 217 upward to and downward from the process
furnace 202. An arm 128 is connected to an elevating table of the boat
elevator 115, and a seal cap 219 is horizontally attached to the arm 128.
The seal cap 219 supports the boat 217 vertically, and is configured be
seal the bottom side of the process furnace 202.

[0051]The boat 217 includes a plurality of holding members, and is
configured to hold a plurality of wafers 200 (for example, about fifty to
one hundred fifty wafers) horizontally in a state that the wafers 200 are
vertically arranged with the centers of the wafers 200 being aligned.

[0052]At the upside of the cassette shelf 105, a cleaning system 134a is
installed to supply clean air as purified atmosphere. The cleaning system
134a includes a supply fan and a dust filter to supply clean air to the
inside of the case 111.

[0053]At the left side end part of the case 111, another cleaning system
134b is installed to supply clean air. The cleaning system 134b includes
a supply fan and a dust filter to supply clean air to the surrounding
area of the wafer transfer device 125a, the boat 217, or the like. After
flowing around the wafer transfer device 125a, the boat 217 or the like,
clean air is exhausted to the outside of the case 111.

[0054]Next, a main operation of the substrate processing apparatus 101
will be described.

[0055]A cassette 110 carried to the cassette stage 114 by the in-plant
carrying unit (not shown) is placed on the cassette stage 114 in a state
where wafers 200 inside the cassette 110 are vertically positioned and
the wafer hole of the cassette 110 is pointed upward. Thereafter, the
cassette 110 is rotated counterclockwise by 90° in a longitudinal
direction toward the backward of the case 111 by the cassette stage 114
so that the wafers 200 inside the cassette 110 are horizontally
positioned and the wafer hole of the cassette 110 is pointed to the
backward of the case 111.

[0056]Then, the cassette 110 is automatically carried and placed by the
cassette carrying device 118 to a specified shelf position of the
cassette shelf 105 or the standby cassette shelf 107 so as to be
temporarily stored, and is then transferred to the transfer shelf 123
from the cassette shelf 105 or the standby cassette shelf 107 by the
cassette carrying device 118. Alternatively, the carry cassette 110 may
be directly transferred to the transfer shelf 123 from the cassette stage
114.

[0057]After the cassette 110 is transferred to the transfer shelf 123,
wafers 200 are picked up from the cassette 110 through the wafer hole of
the cassette 110 and are charged into the boat 217 by the tweezers 125c
of the wafer transfer device 125a. After delivering the wafer 200 to the
boat 217, the wafer transfer device 125a returns to the cassette 110 so
as to charge the next wafers 200 into the boat 217.

[0058]After a predetermined number of wafers 200 are charged into the boat
217, the bottom side of the process furnace 202 closed by the furnace
port shutter 147 is opened by moving the furnace shutter 147.
Subsequently, the boat 217 holding a group of wafers 200 is loaded into
the process furnace 202 by an ascending motion of the boat elevator 115,
and the bottom side of the process furnace 202 is closed by the seal cap
219.

[0059]After the loading, a predetermined heat treatment process is
performed on the wafers 200 charged in the process furnace 202.
Thereafter, the wafers 200 and the cassette 110 are carried to the
outside of the case 111 in a reverse sequence of the above.

[0060][Structure of Process Furnace]

[0061]Next, the structure of the process furnace 202 will be described.
FIG. 2 is a schematic view illustrating an example of the process furnace
202 and surrounding members that can be properly used according to an
embodiment of the present invention, in which a vertical section of the
process furnace 202 is illustrated. FIG. 3 is a sectional view taken
along line A-A of the process furnace 202 of FIG. 2.

[0062]As shown in FIG. 2 and FIG. 3, at the process furnace 202, a heater
207 is installed to heat wafers 200. The heater 207 includes an
insulating member having a cylindrical shape with a closed top side, and
a plurality of heating wires installed with reference to the insulating
member to form a heating system structure.

[0064]At the lower end of the reaction tube 203, a manifold 209 made of a
material such as stainless steel is installed in a manner such that an
O-ring 220 is disposed therebetween as a sealing member. A lower end
opening of the manifold 209 is tightly sealed by a cap such as the seal
cap 219 with an O-ring 220 being disposed between the manifold 209 and
the seal cap 219. The seal cap 219 is made of a metal such as stainless
steel and has a disk shape. In the process furnace 202, a process chamber
201 is formed at least by the reaction tube 203, the manifold 209, and
the seal cap 219.

[0065]At the seal cap 219, a boat support 218 is installed to support the
boat 217. The boat support 218 is made of a heat-resistant material such
as quartz or silicon carbide. The boat support 218 functions as an
insulator as well as a supporting body that supports the boat 217. As
shown in FIG. 1, the boat 217 includes a bottom plate 210 fixed to the
boat support 218, a top plate 211 disposed at the stop side of the boat
217, and a plurality of pillars 212 installed between the bottom plate
210 and the top plate 211. In the boat 217, a plurality of wafers 200 are
held. The plurality of wafers 200 are supported by the pillars 212 of the
boat 217 in a state where the wafers 200 are arranged at regular
intervals and horizontally oriented.

[0066]At the above-described process furnace 202, in a state where a
plurality of wafers 200 to be batch-processed are piled in multiple
states inside the boat 217, the boat 217 is inserted into the process
chamber 201 while being supported by the boat support 218, and then the
heater 207 heats the wafers 200 inserted in the process chamber 201 to a
predetermined temperature.

[0067]As shown in FIG. 2 and FIG. 3, two source gas supply pipes 310 and
320, and a catalyst supply pipe 330 are connected to the process chamber
201.

[0068]At the source gas supply pipe 310, a mass flow controller 312 and a
valve 314 are installed. A nozzle 410 is connected to the leading end of
the source gas supply pipe 310. The nozzle 410 is installed through the
manifold 209 constituting the process chamber 201, and in an arc-shaped
space between the inner wall of the reaction tube 203 and wafers 200, the
nozzle 410 extends vertically along the inner wall of the reaction tube
203. A plurality of gas supply holes 410a are formed in the lateral side
of the nozzle 410 to supply a source gas through the gas supply holes
410a. The sizes of the gas supply holes 410a are equal or varied from the
lower side to the upper side, and the gas supply holes 410a are arranged
at the same pitch. In addition, a carrier gas supply pipe 510 is
connected to the source gas supply pipe 310 to supply a carrier gas. At
the carrier gas supply pipe 510, a mass flow controller 512 and a valve
514 are installed. A first source gas supply system is formed mainly by
the source gas supply pipe 310, the mass flow controller 312, the valve
314, and the nozzle 410.

[0069]In addition, a first carrier gas supply system is formed mainly by
the carrier gas supply pipe 510, the mass flow controller 512, and the
valve 514.

[0070]At the source gas supply pipe 320, a mass flow controller 322 and a
valve 324 are installed. A nozzle 420 is connected to the leading end of
the source gas supply pipe 320. Like the nozzle 410, the nozzle 420 is
installed through the manifold 209 constituting the process chamber 201,
and in the arc-shaped space between the inner wall of the reaction tube
203 and the wafers 200, the nozzle 420 extends vertically along the inner
wall of the reaction tube 203. A plurality of gas supply holes 420a are
formed in the lateral side of the nozzle 420 to supply a source gas
through the gas supply holes 420a. Like the gas supply holes 410a, the
sizes of the gas supply holes 420a are equal or varied from the lower
side to the upper side, and the gas supply holes 420a are arranged at the
same pitch. In addition, a carrier gas supply pipe 520 is connected to
the source gas supply pipe 320 to supply a carrier gas. At the carrier
gas supply pipe 520, a mass flow controller 522 and a valve 524 are
installed. A second source gas supply system is formed mainly by the
source gas supply pipe 320, the mass flow controller 322, the valve 324,
and the nozzle 420. In addition, a second carrier gas supply system is
formed mainly by the carrier gas supply pipe 520, the mass flow
controller 522, and the valve 524.

[0071]At the catalyst supply pipe 330, a mass flow controller 332 and a
valve 334 are installed. A nozzle 430 is connected to the leading end of
the catalyst supply pipe 330. Like the nozzle 410, the nozzle 430 is
installed through the manifold 209 constituting the process chamber 201,
and in the arc-shaped space between the inner wall of the reaction tube
203 and the wafers 200, the nozzle 430 extends vertically along the inner
wall of the reaction tube 203. A plurality of catalyst supply holes 430a
are formed in the lateral side of the nozzle 430 to supply a catalyst
through the catalyst supply holes 430a. Like the gas supply holes 410a,
the sizes of the catalyst supply holes 430a are equal or varied from the
lower side to the upper side, and the catalyst supply holes 430a are
arranged at the same pitch. A carrier gas supply pipe 530 is connected to
the catalyst supply pipe 330 to supply a carrier gas. At the carrier gas
supply pipe 530, a mass flow controller 532 and a valve 534 are
installed. A catalyst supply system is formed mainly by the catalyst
supply pipe 330, the mass flow controller 332, the valve 334, and the
nozzle 430. In addition, a third carrier gas supply system is formed
mainly by the carrier gas supply pipe 530, the mass flow controller 532,
and the valve 534.

[0072]In the above-described structure, for example, a silicon (Si) source
(such as TCS: trichloro silane (SiHCl4) or HCD: hexachloro disilane
(Si2Cl6)) is introduced into the source gas supply pipe 310 as
an example of a metal source gas. For example, an oxidizing gas such as
H2O or H2O2 is introduced into the source gas supply pipe
320. A catalyst such as NH3 is introduced into the catalyst supply
pipe 330.

[0073]An exhaust pipe 231 is connected to the process chamber 201 to
exhaust the inside atmosphere of the processing chamber 201. A vacuum
exhaust device such as a vacuum pump 246 is connected to the process
chamber 201, and a pressure detector (pressure detecting unit) such as a
pressure sensor 245 configured to detect the inside pressure of the
process chamber 201 and a pressure regulator (pressure regulating unit)
such as an auto pressure controller (APC) valve 243e are disposed between
the process chamber 201 and the vacuum pump 246, so that the inside of
the process chamber 201 can be evacuated to a predetermined pressure
(vacuum degree). The APC value 243e is an on/off value, which is
configured to be opened and closed for starting and stopping evacuation
of the processing chamber 201 and be adjusted in opening size for
controlling the inside pressure of the process chamber 201. An exhaust
system is formed mainly by the exhaust pipe 231, the APC valve 243e, the
vacuum pump 246, and the pressure sensor 245.

[0074]At the center part inside the reaction tube 203, the boat 217 is
installed. The boat 217 is configured to be lifted into and lowered away
from the reaction tube 203 by the boat elevator 115. At the bottom side
of the boat support 218 on which the boat 217 is supported, a boat
rotating mechanism 267 is installed to rotate the boat 217 for improving
processing uniformity. A rotation shaft 255 of the boat rotating
mechanism 267 is connected to the boat 217 through the seal cap 219 so
that the boat 217 supported by the boat support 218 can be rotated by
operating the boat rotating mechanism 267 so as to rotate wafers 200
charged in the boat 217.

[0075]In the reaction tube 203, a temperature detector such as a
temperature sensor 263 is installed, and by controlling power supplied to
the heater 207 based on temperature information detected by the
temperature sensor 263, desired temperature distribution can be obtained
in the process chamber 201. Like the nozzles 410, 420, and 430, the
temperature sensor 263 has an L-shape and is disposed along the inner
wall of the reaction tube 203.

[0076]A controller 280 is connected to the above-described members such as
the mass flow controllers 312, 322, 332, 512, 522, and 532, the valves
314, 324, 334, 514, 524, and 534, the APC valve 243e, the heater 207, the
temperature sensor 263, the pressure sensor 245, the vacuum pump 246, the
boat rotating mechanism 267, and the boat elevator 115. For example, the
controller 280 is a control unit that controls the overall operation of
the substrate processing apparatus 101. The controller 280 is configured
to control operations such as flowrate adjusting operations of the mass
flow controllers 312, 322, 332, 512, 522, and 532; opening and closing
operations of the valves 314, 324, 334, 514, 524, and 534; opening,
closing, and pressure adjusting operations of the APC valve 243e; a
temperature adjusting operation of the heater 207; operations of the
temperature sensor 263 and the pressure sensor 245; start and stop
operations of the vacuum pump 246; a rotation speed adjusting operation
of the boat rotating mechanism 267; an elevating operation of the boat
elevator 115.

[0077][Method of Manufacturing Semiconductor Device]

[0078]Next, an explanation will be given on a method of forming an
insulating film on a substrate by using the process furnace 202 of the
substrate processing apparatus 101 in a semiconductor device
manufacturing process such as a large scale integration (LSI) circuit
manufacturing process.

[0079]In the following description, operations of parts of the substrate
processing apparatus 101 are controlled by the controller 280.

[0080]In the current embodiment, an explanation will be given on an
exemplary method of forming a film on a substrate by an atomic layer
deposition (ALD) method. In the ALD method which is a kind of chemical
vapor deposition (CVD) method, process gases including at least two kinds
of materials constituting a film are alternately supplied to a substrate
under predetermined film formation conditions (temperature, time, etc.),
and the process gases are adsorbed on the substrate on an atomic layer
basis to form a film by a surface reaction. In this time, the thickness
of the film is controlled by adjusting the number of process gas supply
cycles (for example, if the film-forming rate is 1 Å/cycle and it is
intended to form a 20-Å film, the process is repeated for twenty
cycles).

First Embodiment

[0081]In the current embodiment, an explanation will be given on an
example of forming a silicon oxide film on a substrate as an insulating
film by using trichloro silane (SiCl4) as a silicon-containing gas,
water (H2O) as an oxidizing gas, and ammonia (NH3) as a
catalyst. NH3 is used as a catalyst because a nitrogen (N) atom of a
NH3 molecule has a lone pair of electrons that attracts hydrogen
(H). The degree of a force attracting hydrogen is expressed by an acid
dissociation constant (pKa), and NH3 has a pKa of about
11. A large pKa means a strong hydrogen attracting force, and
NH3 has such characteristics. FIG. 4 is a view illustrating a
relationship between film-forming rate and film-forming temperature when
a silicon film is formed using NH3 as a catalyst. In FIG. 4, the
film-forming temperature means the inside temperature of the process
chamber 201. As shown in FIG. 4, a film can be formed at a temperature of
about 200° C. or lower, and the film-forming rate increases as the
film-forming temperature decreases.

[0082]FIG. 5 is a view illustrating a sequence for forming a silicon oxide
film using NH3 as a catalyst, and FIG. 6A and FIG. 6B are views
illustrating models of silicon oxide film formation when NH3 is used
as a catalyst. FIG. 7 is a view illustrating pressure variations in the
process chamber 201 during a film-forming process. Hereinafter, with
reference to FIG. 5, FIG. 6A, and FIG. 6B, a film-forming method will be
described in detail according to the current embodiment.

[0083]In a film-forming process, the controller 280 controls the substrate
processing apparatus 101 as follows. The controller 280 controls the
heater 207 to keep the inside temperature of the process chamber 201, for
example, in the range from room temperature to 200° C., preferably
from room temperature to 150° C., more preferably at 100°
C. Then, a plurality of wafers 200 are charged into the boat 217, and the
boat 217 is loaded into the process chamber 201.

[0084]Thereafter, the boat 217 is rotated by the boat rotating mechanism
267 to rotate the wafers 200. Then, the vacuum pump 246 is operated and
the APC valve 243e is opened to evacuate the inside of the process
chamber 201, and if the temperature of the wafers 200 reaches 100°
C. and processing conditions become stable, the following four steps are
sequentially performed while maintaining the inside temperature of the
process chamber 201 at 100° C.

[0085](Step 11)

[0086]In a state where SiCl4 is introduced into the source gas supply
pipe 310, H2O is introduced into the source gas supply pipe 320, a
NH3 catalyst is introduced into the catalyst supply pipe 330, and
N2 is introduced into the carrier gas supply pipes 510, 520, and
530, the valves 314, 334, 514, 524, and 534 are properly opened. However,
the valve 324 is not opened.

[0087]As a result, as shown in FIG. 5, SiCl4 is mixed with N2
and flows to the nozzle 410 from the source gas supply pipe 310, and is
supplied to the process chamber 201 through the gas supply holes 410a. In
addition, a NH3 catalyst is mixed with N2 and flows to the
nozzle 430 from the catalyst supply pipe 330, and is supplied to the
process chamber 201 through the catalyst supply holes 430a. In addition,
N2 flows to the nozzle 420 from the carrier gas supply pipe 520, and
is supplied to the process chamber 201 through the gas supply holes 420a.
Inside the process chamber 201, the SiCl4 and NH3 catalyst flow
along the surfaces of the wafers 200 and are exhausted through the gas
exhaust pipe 231.

[0088]In step 11, the valves 314 and 334 are controlled to supply
SiCl4 and NH3 catalyst for 1 second to 100 seconds, preferably,
5 seconds to 30 seconds. In addition, the valves 314 and 334 are
controlled to keep constant the flowrate ratio (volume flowrate ratio) of
SiCl4 and NH3 catalyst. For example, the flowrate ratio of
SiCl4 (sccm)/NH3 (sccm) is kept at 0.01 to 100, preferably at
0.05 to 10. At the same time, the APC valve 243e is properly controlled
to adjust the inside pressure of the process chamber 201 to an optimal
value in a predetermined range (for example, 10 Torr in FIG. 7).

[0089]As described above, in step 11, SiCl4 and NH3 catalyst are
supplied to the inside of the process chamber 201 to cause NH3
catalyst to act on OH bonds adsorbed on the silicon (Si) substrate (wafer
200) for extracting hydrogen (H) as shown in FIG. 6A. That is, OH bonds
are weakened, and thus Cl of SiCl4 reacts with H to produce HCl gas
(released) and form a halide adsorbed on the Si substrate.

[0090](Step 12)

[0091]The valves 314 and 334 are closed to interrupt supply of SiCl4
and NH3 catalyst but the carrier gas supply pipes 510, 520, and 530
are not closed to supply N2 gas continuously to the inside of the
process chamber 201 for purging the process chamber 201 with N2. The
purging is carried out for 15 seconds, for example. Alternatively,
purging and vacuum evacuation may be performed within 15 seconds. As a
result, remaining SiCl4 and NH3 catalyst are removed from the
process chamber 201.

[0092](Step 13)

[0093]In a state where the valves 514, 524, and 534 are opened, the valves
324 and 334 are properly opened. The valve 314 is closed. Then, as shown
in FIG. 5, H2O is mixed with N2 and flows to the nozzle 420
from the source gas supply pipe 320, and is supplied to the process
chamber 201 through the gas supply holes 420a. In addition, a NH3
catalyst is mixed with N2 and flows to the nozzle 430 from the
catalyst supply pipe 330, and is supplied to the process chamber 201
through the catalyst supply holes 430a.

[0094]In addition, N2 flows to the nozzle 410 from the carrier gas
supply pipe 510, and is supplied to the process chamber 201 through the
gas supply holes 410a. Inside the process chamber 201, the H2O and
NH3 catalyst flow along the surfaces of the wafers 200 and are
exhausted through the gas exhaust pipe 231.

[0095]In step 13, the valves 324 and 334 are controlled to supply H2O
and NH3 catalyst for 1 second to 100 seconds, preferably, 5 seconds
to 30 seconds. In addition, the valves 324 and 334 are controlled to keep
constant the flowrate ratio (volume flowrate ratio) of H2O and
NH3 catalyst. For example, the flowrate ratio of H2O
(sccm)/NH3 (sccm) is kept at 0.01 to 100, preferably at 0.05 to 10.
At the same time, the APC valve 243e is properly controlled to adjust the
inside pressure of the process chamber 201 to an optimal value in a
predetermined range (for example, 10 Torr in FIG. 7).

[0096]As described above, in step 13, H2O and NH3 catalyst are
supplied to the inside of the process chamber 201 to cause NH3
catalyst to act on OH bonds of H2O as shown in FIG. 6B. Similarly,
as OH bonds are weakened, the OH bonds react with chlorine (Cl) adsorbed
on the Si substrate (wafer 200) to produce HCl (released), and O is
adsorbed. Here, preferably, it may be controlled to maintain the weight
percent of H2O similar to the weight percent of NH3 catalyst.

[0097](Step 14)

[0098]The valves 324 and 334 are closed to interrupt supply of H2O
and NH3 catalyst but the carrier gas supply pipes 510, 520, and 530
are not closed to supply N2 gas continuously to the inside of the
process chamber 201 for purging the process chamber 201 with N2. The
purging is carried out for 15 seconds, for example. Alternatively,
purging and vacuum evacuation may be performed within 15 seconds. As a
result, remaining H2O and NH3 catalyst are removed from the
process chamber 201.

[0099]Thereafter, steps 11 to step 14 are repeated for a plurality of
cycles to form silicon oxide films on the wafers 200 to a predetermined
thickness. In each cycle, it is necessary to perform the process in a
manner such that the atmosphere of step 11 formed by a silicon-containing
gas and a catalyst is not mixed with the atmosphere of step 13 formed by
an oxidizing gas and a catalyst in the process chamber 201. In this way,
silicon oxide films are formed on the wafers 200.

[0100]Thereafter, the process chamber 201 is vacuum-evacuated to exhaust
remaining SiCl4, H2O, and NH3 catalyst; the inside
pressure of the process chamber 201 is adjusted to atmospheric pressure
by controlling the APC valve 243e; and the boat 217 is unloaded from the
process chamber 201. In this way, the film-forming process (batch
process) is performed one time.

[0101]In the above description, SiCl4 is used as a silicon-containing
gas (metal-containing gas); however, other sources gases may be used.
Examples of sources gases that can be used as a silicon-containing gas
include: chlorine (Cl)-based source gases such as hexachlorodisilane
(HCD: Si2Cl6), trichlorosilane (TCS: SiHCl3),
trisdimethylaminosilane (TDMAS: SiH(N(CH3)2)3),
dichlorosilane (DCS: SiH2Cl2), octachlorotrisilane
(Si3Cl8), trichloromethylsilane ((CH3)SiCl3);
fluorine (F)-based source gases such as SiF4 and Si2F6;
SiI4; and SiBr4. That is, a silicon-containing fluoride, a
silicon-containing bromide, or a silicon-containing iodide may also be
used as a silicon-containing gas. However, a compound containing chlorine
and an alkyl group such as SiCl3(CH3) may not be suitable
because the film-forming rate can be decreased by steric hinderance
caused by the alkyl group. Compounds such as chlorides, fluorides,
bromides, and iodides may be preferable, and a silicon compound to which
hydrogen (H) is partially coupled may be more preferable. For example,
SiH2Cl2 may be more preferable. A metal-containing substance
having a double bond such as Si2Cl2 may also be used.

[0102]In addition, H2O is used as an oxidizing gas; however, other
oxidizing gases may be used. Such oxidizing gases are required to have
electric polarity which is presented by an atom having electronegativity
different from that of another element in a molecule. The reason for this
requirement is that a catalyst acts on electrically polar molecules to
reduce the activation energy of a source gas. Therefore, for example,
H2O or H2O2 having an OH bond, H2+O2 mixture
plasma, or H2+O3 may be used as an oxidizing gas. However,
non-polar molecules such as O2 or O3 are not suitable.

[0103]NH3 is used as a catalyst; however, other gases can be used.
For example, trimethylamine (N(CH3)3, pKa=9.8),
methylamine (H2N(CH3), pKa=10.6), or triethylamine
(N(C2H5)3, pKa=10.7) may be used. FIG. 8 shows
structures of such substances. The acid dissociation constant pKa of
the substances range from 9.8 to 10.7, and the acid dissociation constant
pKa, of NH3 is about 9.2.

[0104]As described above, a film can be formed at a low temperature by
using NH3 catalyst; however, since SiCl4 is supplied together
with the NH3 catalyst as shown in FIG. 6A, the NH3 catalyst
itself can react with Cl of SiCl4 to produce NH4Cl as a
reaction byproduct. Such a byproduct may become particles and undesirably
affect a semiconductor device manufacturing process.

[0105]Although trimethylamine (N(CH3)3, pKa=9.8),
methylamine (H2N(CH3), pKa=10.6), or triethylamine
(N(C2H5)3, pKa=10.7) is used instead of NH3,
generation of particles cannot be reduced. This is caused by a low vapor
pressure of NH4Cl.

[0106]FIG. 9 is a view illustrating a vapor pressure curve of NH4Cl.
Generally, NH4Cl is in a gaseous (vapor) state at a pressure lower
than its vapor pressure. That is, NH4Cl particles do not exit. In
addition, NH4Cl is in a solid state at a pressure higher than its
vapor pressure. That is, NH4Cl particles exist. Here, solid may mean
particles.

[0107]Meanwhile, as shown in FIG. 7, in steps 11 to 13, the inside
pressure of the process chamber 201 increases up to 10 Torr, and the
inside temperature of the process chamber 201 ranges from room
temperature to 200° C., preferable at 100° C. At
100° C., the vapor pressure of NH4Cl is 5 Pa (0.04 Torr)
lower than the film-forming pressure of 10 Torr, so that NH4Cl is
adsorbed as solid. Undesirably, such solid may generate particles.

[0108]As described above, use of NH3 as a catalyst makes it possible
to form a film at a low temperature; however, in this case, it is
required to prevent generation of particles.

[0109]Next, an explanation will be given on a method of forming a film at
a low temperature by using a catalyst generating fewer particles to
overcome limitations of the first embodiment.

Second Embodiment

[0110]It is necessary to prevent direct reaction between Cl (chlorine) and
a catalyst for suppressing generation of particles. Generally, a
substance having high acid dissociation constant tends to actively react
with a substance including a group 17 element such as chlorine (Cl).
Therefore, to suppress generation of particles, it is necessary to select
a substance having low acid dissociation constant. For example, pyridine
(C5H5N, pKa=5.7) is selected. In addition, SiCl4
(trichlorosilane) is used as a silicon-containing gas, and H2O
(wafer) is used as an oxidizing gas. This exemplary case will now be
described.

[0111]Furthermore, generation of particles can be reduced by setting the
inside pressure of the process chamber 201 to a level lower than the
vapor pressure of a byproduct generating after a film-forming process.
However, if the inside pressure of the process chamber 201 is excessively
low, the film-forming rate may be reduced to lower throughput. Therefore,
preferably, a catalyst is selected on the basis that a byproduct
generating after a film-forming process has a sufficiently high vapor
pressure so as not to affect the throughput.

[0112]FIG. 10 is a view illustrating a sequence for forming a film
according to the current embodiment, and FIG. 15 is a view illustrating
film-forming models when pyridine is used as a catalyst.

[0113]In a film-forming process, the controller 280 controls the substrate
processing apparatus 101 as follows. The controller 280 controls the
heater 207 to keep the inside temperature of the process chamber 201, for
example, in the range from room temperature to 200° C., preferably
from room temperature to 150° C., more preferably at 100°
C. Then, a plurality of wafers 200 are charged into the boat 217, and the
boat 217 is loaded into the process chamber 201. Thereafter, the boat 217
is rotated by the boat rotating mechanism 267 to rotate the wafers 200.
Then, the vacuum pump 246 is operated and the APC valve 243e is opened to
evacuate the inside of the process chamber 201, and if the temperature of
the wafers 200 reaches 100° C. and processing conditions become
stable, the following four steps are sequentially performed while
maintaining the inside temperature of the process chamber 201 at
100° C.

[0114](Step 21)

[0115]In a state where SiCl4 is introduced into the source gas supply
pipe 310, H2O is introduced into the source gas supply pipe 320,
pyridine is introduced into the catalyst supply pipe 330, and N2 is
introduced into the carrier gas supply pipes 510, 520, and 530, the
valves 314, 334, 514, 524, and 534 are properly opened. However, the
valve 324 is not opened.

[0116]As a result, as shown in FIG. 10, SiCl4 is mixed with N2
and flows to the nozzle 410 from the source gas supply pipe 310, and is
supplied to the process chamber 201 through the gas supply holes 410a. In
addition, pyridine is mixed with N2 and flows to the nozzle 430 from
the catalyst supply pipe 330, and is supplied to the process chamber 201
through the catalyst supply holes 430a. In addition, N2 flows to the
nozzle 420 from the carrier gas supply pipe 520, and is supplied to the
process chamber 201 through the gas supply holes 420a. Inside the process
chamber 201, the SiCl4 and pyridine flow along the surfaces of the
wafers 200 and are exhausted through the gas exhaust pipe 231.

[0117]In step 21, the valves 314 and 334 are controlled to supply
SiCl4 and pyridine for 1 second to 100 seconds, preferably, 5
seconds to 30 seconds. Here, the relationship between supply time of
SiCl4 and pyridine and film thickness is shown in FIG. 11. As the
supply time of SiCl4 increases, the film thickness increases;
however, if the supply time increases equal to or longer than 15 seconds,
the film thickness is not varied. This is due to saturation of a surface
adsorption reaction. That is, since the amount of source gas supplied at
or after 15 seconds from the start of supply is uselessly consumed, it is
not cost effective. Since the saturation time at which the surface
adsorption reaction is saturated is dependent on the size of the process
chamber 201 and the number of wafers 200, the saturation time can be
varied from 15 seconds, and thus it may be necessary to properly adjust
the supply time, for example, in the range from 5 seconds to 30 seconds.

[0118]In addition, the valves 314 and 334 are controlled to keep constant
the flowrate ratio (volume flowrate ratio) of SiCl4 and pyridine.
For example, the flowrate ratio of SiCl4 (sccm)/pyridine (sccm) is
kept at 0.01 to 100, preferably at 0.05 to 10. FIG. 12 is a view
illustrating a film thickness obtained by supplying SiCl4 at a
constant rate of 500 sccm while supplying pyridine at a varying rate. The
film thickness increases as the supply flowrate of pyridine increases;
however, the supply flowrate of pyridine increases equal to or greater
than 750 sccm, the film thickness is not increased. In the experiment,
the flowrate ratio of SiCl4/pyridine is optimal at 500/750=0.66;
however, it may be properly adjusted according to the size of the process
chamber 201 and the number of wafers 200, for example, in the range from
0.05 to 10. At the same time, the APC valve 243e is properly controlled
to adjust the inside pressure of the process chamber 201 to an optimal
value in a predetermined range (for example, 10 Torr). Here, the inside
pressure of the process chamber 201 is set to a level lower than the
vapor pressure of a byproduct that can be produced after a film-forming
process.

[0119]As described above, SiCl4 and pyridine are supplied to the
inside of the process chamber 201 to cause pyridine to act on OH bonds
adsorbed on the silicon (Si) substrate (wafer 200) for extracting
hydrogen (H) as shown in FIG. 15. That is, OH bonds are weakened, and
thus Cl of SiCl4 reacts with H to produce HCl gas (released) and
form a halide adsorbed on the Si substrate.

[0120](Step 22)

[0121]The valves 314 and 334 are closed to interrupt supply of SiCl4
and pyridine but the carrier gas supply pipes 510, 520, and 530 are not
closed to supply N2 gas continuously to the inside of the process
chamber 201 for purging the process chamber 201 with N2. The purging
is carried out for 15 seconds, for example. Alternatively, purging and
vacuum evacuation may be performed within 15 seconds. As a result,
remaining SiCl4 and pyridine are removed from the process chamber
201.

[0122](Step 23)

[0123]In a state where the valves 514, 524, and 534 are opened, the valves
324 and 334 are properly opened. The valve 314 is closed. Then, as shown
in FIG. 10, H2O is mixed with N2 and flows to the nozzle 420
from the source gas supply pipe 320, and is supplied to the process
chamber 201 through the gas supply holes 420a. In addition, pyridine is
mixed with N2 and flows to the nozzle 430 from the catalyst supply
pipe 330, and is supplied to the process chamber 201 through the catalyst
supply holes 430a. In addition, N2 flows to the nozzle 410 from the
carrier gas supply pipe 510, and is supplied to the process chamber 201
through the gas supply holes 410a. Inside the process chamber 201, the
H2O and pyridine flow along the surfaces of the wafers 200 and are
exhausted through the gas exhaust pipe 231.

[0124]In step 23, the valves 324 and 334 are controlled to supply H2O
and pyridine for 1 second to 100 seconds, preferably, 5 seconds to 30
seconds. Here, the relationship between supply time of H2O and
pyridine and film thickness is shown in FIG. 13. As the supply time of
H2O increases, the film thickness increases; however, if the supply
time increases equal to or longer than 14 seconds, the film thickness is
not varied. This is due to saturation of a surface adsorption reaction.
That is, since the amount of source gas supplied at or after 14 seconds
from the start of supply is uselessly consumed, it is not cost effective.
Since the saturation time at which the surface adsorption reaction is
saturated is dependent on the size of the process chamber 201 and the
number of wafers 200, the saturation time can be varied from 14 seconds,
and thus it may be necessary to properly adjust the supply time, for
example, in the range from 5 seconds to 30 seconds

[0125]In addition, the valves 324 and 334 are controlled to keep constant
the flowrate ratio (volume flowrate ratio) of H2O and pyridine. For
example, the flowrate ratio of H2O (sccm)/pyridine (sccm) is kept at
0.01 to 100, preferably at 0.05 to 10. FIG. 14 is a view illustrating a
film thickness obtained by supplying H2O at a constant rate of 2000
sccm while supplying pyridine at a varying rate. The film thickness
increases as the supply flowrate of pyridine increases; however, the
supply flowrate of pyridine increases equal to or greater than 800 sccm,
the film thickness is not increased. In the experiment, the flowrate
ratio of H2O/pyridine is optimal at 2000/800=2.5; however, it may be
properly adjusted according to the size of the process chamber 201 and
the number of wafers 200, for example, in the range from 0.05 to 10.

[0126]At the same time, the APC valve 243e is properly controlled to
adjust the inside pressure of the process chamber 201 to an optimal value
in a predetermined range (for example, 10 Torr). As described above, in
step 23, H2O and pyridine are supplied to the inside of the process
chamber 201 to cause pyridine to act on OH bonds of H2O as shown in
FIG. 15. Similarly, as OH bonds are weakened, the OH bonds react with
chlorine (Cl) adsorbed on the Si substrate (wafer 200) to produce HCl
(released), and O is adsorbed. Here, preferably, it may be controlled to
maintain the weight percent of H2O similar to the weight percent of
pyridine.

[0127](Step 24)

[0128]The valves 324 and 334 are closed to interrupt supply of H2O
and pyridine but the carrier gas supply pipes 510, 520, and 530 are not
closed to supply N2 gas continuously to the inside of the process
chamber 201 for purging the process chamber 201 with N2. The purging
is carried out for 15 seconds, for example. Alternatively, purging and
vacuum evacuation may be performed within 15 seconds. As a result,
remaining H2O and pyridine are removed from the process chamber 201.

[0129]Thereafter, steps 21 to step 24 are repeated for a plurality of
cycles to form silicon oxide films on the wafers 200 to a predetermined
thickness. In each cycle, it is necessary to perform the process in a
manner such that the atmosphere of step 21 formed by a silicon-containing
gas and a catalyst is not mixed with the atmosphere of step 23 formed by
an oxidizing gas and a catalyst in the process chamber 201. In this way,
silicon oxide films are formed on the wafers 200.

[0130]After silicon oxide films are formed on the wafers 200 to a
predetermined thickness, the inside pressure of the process chamber 201
is adjusted to atmospheric pressure by controlling the APC valve 243e,
and the boat 217 is unloaded from the process chamber 201. In this way,
the film-forming process (batch process) is performed one time.

[0131]In the above description, SiCl4 is used as a silicon-containing
gas, and H2O is used as an oxidizing gas; however, other source
gases and other oxidizing gases may be used as described in the first
embodiment.

[0132]FIG. 16 is a view showing numbers of particles on a wafer 200 for
the case where NH3 is used as a catalyst and the case where pyridine
is used as a catalyst. In both cases, the process temperature of the
film-forming sequence is kept at 100° C. Referring to FIG. 16,
when pyridine is used as a catalyst, the number of particles can be
reduced.

[0133]In the case where pyridine is used as a catalyst, it is considered
that particles are generated from a solidified pyridine salt (reaction
byproduct). FIG. 17 is a view illustrating a vapor pressure curve of a
pyridine salt. At 100° C., the vapor pressure of the pyridine salt
is 14 Torr which is higher than the film-forming pressure. A reaction
byproduct having a vapor pressure higher than the film-forming pressure
may not be disadvantageously treated as a source of particles. If a wafer
on which pyridine salt particles are formed is heat-treated at 10 Torr
and 100° C., the pyridine salt particles may sublimate, and thus
the particles may be reduced.

[0134]Thus, preferably, a catalyst of which a byproduct has a vapor
pressure of 10 Torr or higher at 100° C. may be selected.

[0135]FIG. 18 is a view illustrating the growing rates of oxide films for
the case where NH3 is used as a catalyst and the case where pyridine
is used as a catalyst. Referring to FIG. 18, a film can be formed more
rapidly in the case where pyridine is used as a catalyst than in the case
where NH3 is used as a catalyst. The reason for this may be that
NH4Cl, which a solid byproduct hindering a reaction, does not exist
on the surface of a wafer 200.

[0136]As described above, by using pyridine having acid dissociation
constant pKa smaller than that of NH3 as a catalyst, a film can
be formed at a low temperature, and moreover, generation of particles can
be prevented.

Third Embodiment

[0137]In the second embodiment, pyridine is used as a catalyst. However,
since pyridine causes environmental pollution such as air pollution, the
use of pyridine may be regulated by a law or be reported. A substance
such as picoline has acid dissociation constant pKa similar to that
of pyridine by less regulated by a law. Except for the used of a
different kind of catalyst, the current embodiment is the same as the
second embodiment, and thus a detailed description of the current
embodiment will be omitted.

[0138]Another catalyst having acid dissociation constant pKa of about
5 to about 7 may be used. For example, catalysts such as pyridine,
aminopyridine, picoline, piperazine, and lutidine can be used. Such
substances have similar structures characterized by nitrogen (N) coupled
to a heterocyclic ring. FIG. 19 illustrates structures of such
substances.

[0139]Although substances such as pyrrolidine and piperidine are similar
to the above-described substances, since they have acid dissociation
constant pKa of about 11 and easily produce chlorides, there are not
preferable. FIG. 20 illustrates structures of pyrrolidine and piperidine.

[0140]In addition, although there are other similar substances such as
pyrazine and triazine, since the acid dissociation constant pKa
thereof is too small at about 1 which means a weak hydrogen (H)
attracting force, they are not suitable for being used in a silicon oxide
film forming process. FIG. 21 illustrates structures of pyrazine and
triazine.

[0141]As described above, in an environment where a process chamber is
kept at a low temperature and a film-forming pressure of about 10 Torr so
as to prevent damage of a substrate, the inventors have found that a
catalyst having acid dissociation constant pKa greater than 7 is not
suitable for suppressing generation of a byproduct such as a chloride.

[0142]In addition, the inventors have found that if the acid dissociation
constant pKa of a catalyst is smaller than 5, since a hydrogen (H)
attracting force of the catalyst is weak, the catalyst is not suitable
for forming a silicon oxide film.

[0143]As described above, by selecting a catalyst having acid dissociation
constant pKa in an allowable range, a film can be formed at a low
temperature while preventing generation of particles.

Fourth Embodiment

[0144]An explanation will now be given on the case where a process
temperature is set to 20° C. with other conditions being the same
as those in the second embodiment. Since other conditions are the same as
those of the second embodiment except for the process temperature, a
detailed description of the current embodiment will be omitted. FIG. 22
illustrates filming-forming models, and FIG. 23 is a view for comparing
the number of particles on a wafer 200 in the current embodiment with the
number of particles on a wafer 200 in the second embodiment. It can be
understood that the number of particles increases if the process
temperature is set to 20° C. The reason for this is solidification
of a pyridine salt (reaction byproduct) caused by the low process
temperature of 20° C.

Fifth Embodiment

[0145]In the above-described first to fourth embodiments, a silicon oxide
film is formed on a wafer 200 as an example of a metal thin film. In the
current embodiment, an explanation will be given on the case where a
silicon nitride film is formed on a wafer 200. The current embodiment is
the same as the second embodiment except that a nitriding gas is used as
a modification gas to form a silicon nitride film. Thus, a detailed
description of the current embodiment will be omitted.

[0146]In the current embodiment, NH3 is used as a nitriding gas to
form silicon nitride film instead of a silicon oxide film. By supplying
pyridine used as a catalyst together with a silicon-containing gas, and
an oxidizing gas together with pyridine, a silicon nitride film can be
formed at a low temperature.

[0147]In addition, other nitrogen (N)-containing gases having a NH bond
can be used as a nitriding gas. For example, N2H4,
(CH3)N2H3, or (CH3)N2H2 may be selected as
a nitriding gas.

[0148]In the first to fifth embodiments, a source gas or a modification
gas, and a catalyst are simultaneously supplied for the same time period.
However, they may be supplied at different times as long as a wafer 200
can be exposed to a mixture of the source gas or the modification gas and
the catalyst. That is, for example, a catalyst may be supplied to a
process chamber where a source gas or a modification gas is previously
supplied, or a source gas or a modification gas may be supplied to a
process chamber where a catalyst is previously supplied. Furthermore, in
a state where a source gas or a modification gas and a catalyst are being
supplied, the supply of the source gas or the modification gas may be
first interrupted, and after a predetermined time, the supply of the
catalyst may be interrupted. Alternatively, in that state, the supply of
the catalyst may be first interrupted, and after a predetermined time,
the supply of the source gas or the modification gas may be interrupted.

[0149]When a source gas or a modification gas is supplied together with or
simultaneously with a catalyst, the source gas or the modification gas
and the catalyst may be supplied in a mixed state for only at least a
predetermined time, and supplies of the source gas or modification gas
and the catalyst may be stared at the same time or different times and be
interrupted at the same time or different times. Furthermore, an
exposure-to-source-gas process for exposing a substrate to a source gas,
an exposure-to-modification-gas process for exposing the substrate to an
oxidizing gas or a nitriding gas, and an exposure-to-catalyst process for
exposing the substrate to a catalyst may be performed as follows. The
exposure-to-source-gas process and the exposure-to-catalyst process, or
the exposure-to-modification-gas process and the exposure-to-catalyst
process may be simultaneously performed in a manner such that the
substrate can be exposed to a mixture of the gas and the catalyst for
only a predetermined time. That is, the processes may be starred at the
same time or different times and be terminated at the same time or
different times.

[0150]In the first to fifth embodiments, a silicon oxide film or a silicon
nitride film is formed on a wafer 200 by using a silicon-containing gas
(metal-containing substance) as a thin film forming source gas. However,
other metal-containing substances can be used instead of a
silicon-containing gas. For example, a substance containing a group 4
element and a group 14 element, germanium (Ge), hafnium (Hf), zirconium
(Zr), titanium (Ti), or gallium (Ga) may be used for obtaining the same
effect. A compound may be used, which contains any one of the
above-mentioned elements in combination with the other elements which are
the same as those of a compound mentioned as a silicon-containing gas in
the first embodiment.

[0151]By using such a metal-containing substance and a catalyst, a film
such as a silicon oxide (SiO) film, a germanium oxide (GeO) film, a
titanium oxide (TiO) film, a zirconium oxide (ZrO) film, a hafnium oxide
(HfO) film, a gallium oxide (GaO) film, a silicon nitride (SiN) film, a
germanium nitride (GeN) film, a titanium nitride (TiN) film, a zirconium
nitride (ZrN) film, a hafnium nitride (HfN) film, or a gallium nitride
(GaN) film can be formed on a wafer 200 at a low temperature.

[0152]According to the present invention, when an oxide or nitride film is
formed on a substrate placed in the process chamber by exposing the
substrate to a source gas, one of an oxidizing gas and a nitriding gas,
and a catalyst, since a substance selected as the catalyst has acid
dissociation constant pKa in the range from 5 to 7, the oxide or
nitride film can be formed on the substrate at a low temperature.

[0153][Supplementary Note]

[0154]The present invention also includes the following preferred
embodiments.

[0155](Supplementary Note 1)

[0156]According to an embodiment of the present invention, there is
provided a semiconductor device manufacturing method for forming an oxide
or nitride film on a substrate, the semiconductor device manufacturing
method comprising: exposing the substrate to a source gas; exposing the
substrate to a modification gas comprising an oxidizing gas or a
nitriding gas, wherein an atom has electronegativity different from that
of another atom in molecules of the oxidizing gas or the nitriding gas;
and exposing the substrate to a catalyst, wherein the catalyst has acid
dissociation constant pKa in a range from 5 to 7, but a pyridine is
not used as the catalyst.

[0157](Supplementary Note 2)

[0158]Preferably, the exposing of the substrate to the source gas and the
exposing of the substrate to the catalyst may be simultaneously
performed, and the exposing of the substrate to the modification gas and
the exposing of the substrate to the catalyst may be simultaneously
performed.

[0159](Supplementary Note 3)

[0160]Preferably, the semiconductor device manufacturing method may
further comprise removing the source gas, the oxidizing gas, or the
nitriding gas that remains, wherein the substrate may be exposed to the
source gas, the oxidizing gas, or the nitriding gas in a state where the
source gas and the oxidizing gas or the nitriding gas are not mixed with
each other.

[0161](Supplementary Note 4)

[0162]Preferably, the catalyst may be a heterocyclic compound comprising
nitrogen (N).

[0163](Supplementary Note 5)

[0164]Preferably, the catalyst may be one of aminopyridine, picoline,
piperazine, and lutidine.

[0165](Supplementary Note 6)

[0166]Preferably, the source gas may be a compound comprising one or more
of group 4 elements or group 14 elements.

[0167](Supplementary Note 7)

[0168]Preferably, the source gas may be a compound comprising one or more
of silicon (Si), germanium (Ge), titanium (Ti), zirconium (Zr), hafnium
(Hf), and gallium (Ga).

[0169](Supplementary Note 8)

[0170]Preferably, the oxidizing gas may be a substance having OH bonds,
and the nitriding gas may be a substance having NH bonds.

[0171](Supplementary Note 9)

[0172]Preferably, the oxidizing gas may comprise one or more of H2O,
H2O2, plasma of a mixture of H2 and O2, O2
plasma, H2, and O3.

[0173](Supplementary Note 10)

[0174]Preferably, the oxide or nitride film formed on the substrate may be
one or a compound of a silicon oxide (SiO) film, a germanium oxide (GeO)
film, a titanium oxide (TiO) film, a zirconium oxide (ZrO) film, a
hafnium oxide (HfO) film, a gallium oxide (GaO) film, a silicon nitride
(SiN) film, a germanium nitride (GeN) film, a titanium nitride (TiN)
film, a zirconium nitride (ZrN) film, a hafnium nitride (HfN) film, and a
gallium nitride (GaN) film.

[0175](Supplementary Note 11)

[0176]Preferably, the source gas may be a compound comprising a group 17
element.

[0177](Supplementary Note 12)

[0178]Preferably, the source gas may be a compound comprising one or more
of chlorine (Cl), fluorine (F), bromine (Br), and iodine (I).

[0179](Supplementary Note 13)

[0180]According to another embodiment of the present invention, there is
provided a semiconductor device manufacturing method comprising: exposing
a substrate placed in a process chamber to a source gas; exposing the
substrate placed in the process chamber to a modification gas comprising
an oxidizing gas or a nitriding gas, wherein an atom has
electronegativity different from that of another atom in molecules of the
oxidizing gas or the nitriding gas; and exposing the substrate placed in
the process chamber to a catalyst, wherein the exposing of the substrate
to the source gas, the exposing of the substrate to the modification gas,
and the exposing of the substrate to the catalyst are performed while
heating the substrate, so as to form an oxide or nitride film on the
substrate, wherein in the exposing of the substrate to the catalyst, the
process chamber is kept at a pressure lower than a vapor pressure of a
byproduct corresponding to a surface temperature of the substrate, the
byproduct being produced by a reaction between the catalyst and the
source gas and starting to sublimate at the vapor pressure, wherein the
sublimated byproduct is exhausted to an outside area of the process
chamber.

[0181](Supplementary Note 14)

[0182]Preferably, the process chamber may be kept at a temperature equal
to or lower than 200° C.

[0183](Supplementary Note 15)

[0184]Preferably, the process chamber may be kept at about 100° C.

[0185](Supplementary Note 16)

[0186]Preferably, the exposing of the substrate to the source gas and the
exposing of the substrate to the catalyst may be simultaneously
performed, and the exposing of the substrate to the modification gas and
the exposing of the substrate to the catalyst may be simultaneously
performed, so as to form the oxide or nitride film on the substrate.

[0187](Supplementary Note 17)

[0188]Preferably, the semiconductor device manufacturing method may
further comprise removing an atmosphere from the process chamber, wherein
the substrate placed in the process chamber is exposed to the source gas,
the oxidizing gas, or the nitriding gas in a state where the source gas
and the oxidizing gas or the nitriding gas are not mixed with each other.

[0189](Supplementary Note 18)

[0190]According to another embodiment of the present invention, there is
provided a substrate processing apparatus comprising: a process chamber
configured to accommodate a substrate; a first gas supply system
configured to supply a source gas to the process chamber; a second gas
supply system configured to supply at least one of an oxidizing gas and a
nitriding gas to the process chamber, wherein an atom has
electronegativity different from that of another atom in molecules of the
oxidizing gas and the nitriding gas; a third gas supply system configured
to supply a catalyst to the process chamber, wherein the catalyst has
acid dissociation constant pKa in a range from about 5 to about 7
but a pyridine is not used as the catalyst; and a control unit configured
to control the first to third gas supply systems, wherein the control
unit controls the first to third gas supply systems to expose a surface
of the substrate to a mixture of the source gas and the catalyst and then
to a mixture of the catalyst and at least one of the oxidizing gas and
the nitriding gas, so as to form a oxide or nitride film on the
substrate.

[0191](Supplementary Note 19) According to another embodiment of the
present invention, there is provided a substrate processing apparatus
comprising: a process chamber configured to accommodate a substrate; a
heating system configured to heat the substrate to a predetermined
process temperature; a first gas supply system configured to supply a
source gas to the process chamber; a second gas supply system configured
to supply at least one of an oxidizing gas and a nitriding gas to the
process chamber, wherein an atom has electronegativity different from
that of another atom in molecules of the oxidizing gas and the nitriding
gas; a third gas supply system configured to supply a catalyst to the
process chamber; and a control unit configured to control the heating
system and the first to third gas supply systems, wherein so as to form
an oxide or nitride film on the substrate, the control unit controls the
heating system and the first to third gas supply systems so as to heat
the substrate to a predetermined process temperature and expose a surface
of the substrate to a mixture of the source gas and the catalyst and then
to a mixture of the catalyst and at least one of the oxidizing gas and
the nitriding gas while keeping the process chamber at a pressure lower
than a vapor pressure of a byproduct corresponding to a surface
temperature of the substrate, the byproduct being produced by a reaction
between the catalyst and the source gas and starting to sublimate at the
vapor pressure.

[0192](Supplementary Note 20)

[0193]According to another embodiment of the present invention, there is
provided a semiconductor device on which an oxide or nitride film is
formed by: exposing the substrate to a source gas; exposing the substrate
to a modification gas comprising an oxidizing gas or a nitriding gas; and
exposing the substrate to a catalyst, wherein an atom has
electronegativity different from that of another atom in molecules of the
oxidizing gas or the nitriding gas, and the catalyst has acid
dissociation constant pKa in a range from 5 to 7 but a pyridine is
not used as the catalyst.

[0194](Supplementary Note 21)

[0195]According to another embodiment of the present invention, there is
provided a semiconductor device manufacturing method for forming an oxide
or nitride film on a substrate, the semiconductor device manufacturing
method comprising: exposing the substrate to the source gas; exposing the
substrate to a modification gas comprising an oxidizing gas or a
nitriding gas, wherein an atom has electronegativity different from that
of another atom in molecules of the oxidizing gas or the nitriding gas;
and exposing the substrate to a catalyst, wherein the catalyst has acid
dissociation constant pKa in an allowable range.

[0196](Supplementary Note 22)

[0197]According to another embodiment of the present invention, there is
provided a semiconductor device manufacturing method comprising: a first
process of exposing a substrate placed in a process chamber to a source
gas and a catalyst; a second process of exhausting an inside atmosphere
of the process chamber; a third process of exposing the substrate to an
oxidizing gas or a nitriding gas and a catalyst, wherein an atom has
electronegativity different from that of another atom in molecules of the
oxidizing gas or the nitriding gas; and a fourth process of exhausting
the inside atmosphere of the process chamber, wherein the first to fourth
processes are sequentially performed to form an oxide or nitride film on
the substrate, and a catalyst having acid dissociation constant pKa
in a range from 5 to 7 but not pyridine is used in the second process and
the fourth process.

[0198]Although a vertical batch type apparatus is described, the present
invention is not limited thereto. For example, the present invention can
be applied to a single-wafer type apparatus and a horizontal type
apparatus.

[0199]In addition, according to the present invention, since a film can be
formed at a low temperature at which photoresist is not damaged, the
present invention can be applied to a lithography double patterning
method in which a photoresist pattern is formed by repeating a patterning
process twice or more.